Generally, silver halide color photographic materials contain three types of couplers that couple with the oxidized product of an aromatic primary amine color-developing agent to form yellow, magenta, and cyan dyes.
Of these, yellow couplers that are generally used are acylacetamide couplers, typically benzoylacetanilide couplers and pivaloylacetanilide couplers. Benzoylacetamide couplers have excellent characteristics that the coupling activity thereof to an oxidized product of aromatic primary amine developing agents at the time of development is generally high and the molecular extinction coefficient of the produced yellow dye is large, while they have a defect that the color image fastness during storage in darkness is low. Although pivaloylacetamide couplers are excellent in color image fastness, since the coupling reactivity at the time of development is low and the molecular extinction coefficient is small, a larger amount of the color-forming coupler must be used to obtain an adequate color image density, which is disadvantageous in view of the image quality and cost.
Consequently, development of a yellow coupler having the merits of both, that is, both high color-forming properties (a high coupling activity of the coupler and a high molecular extinction coefficient of the produced dye) and color image fastness is desired.
From the above point of view, acyl groups of acylacetamide couplers have been studied. For example, U.S. Pat. Re No. 27,848 discloses a coupler having a 7,7-dimethylnobornane-1-carbonyl group or a 1-methylcyclohexane-1-carbonyl group as a modification of a pivaloyl group. However, the coupling activity of these couplers is low and the molecular extinction coefficient of the formed dye is small. Further, JP-A ("JP-A" means unexamined published Japanese patent application) No. 26133/1972 discloses a coupler having a cyclopropane-1-carbonyl group or a cyclohexane-1-carbonyl group. However, the fastness of the dye formed from these couplers is low and unsatisfactory.
On the other hand, in color photographic materials, it is considered important to reduce the thickness of the dried coating layer of photographic materials in view of the improvement of image quality, and in particular sharpness. Since, out of photosensitive silver halide layers of photographing materials, particularly the blue-sensitive silver halide layer that uses a yellow coupler constitutes the uppermost layer in many cases, it is considered that the blue-sensitive layer influences greatly the improvement of sharpness of the green-sensitive layer and the red-sensitive layer that underlie the blue-sensitive layer.
Generally, since a coupler is dissolved in a high-boiling organic solvent, is emulsified to disperse it, and is applied on a base, reduction of the amount of the high-boiling solvent employed can be an effective means of making the layer thinner. However, if high-color-forming benzoylacetamide yellow couplers that are conventionally utilized are used, the activity lowers extremely when the amount of a high-boiling organic solvent to be used is decreased, and therefore there is a limit making the layer thinner by this technique.
Pivaloyl acetoaminde couplers low in coupling activity and with low molecular extinction coefficients have by themselves a limit to the thinning of the layer.
To make the layer thin by only lowering the amount of gelatin without decreasing a high-boiling organic solvent is not practical because it greatly deteriorates the layer quality. Generally, the layer quality is greatly influenced by the ratio of oil-soluble substance, including coupler and the high-boiling organic solvent, to gelatin. Consequently, if it is established that the layer quality is to be kept constant, decreasing the oil-soluble substance means that the gelatin can also be decreased at the same time.
Therefore, it follows that the decrease of a high-boiling organic solvent constituting a considerable part of oil-soluble substance is quite effective in making the layer thin.
For the above reasons, development of couplers that give an adequate color density even when the amount of a high-boiling organic solvent to be used is decreased is desired.